I am a little lost on what is going on with this truck. It is a 75 f-150 with a Holley 4160 from the factory. When I purchased it, it was hesistating when giving it gas from a stop and leaking fuel from the passenger side of the carb, but it idled and ran good. So I ordered a carb rebuild kit from some company in canada, and found a replacement vacuum advance on rock auto. I also replaced the spark plugs and cap/rotor and wires. So after installing everything and starting the truck i found it to run like crap at an idle. Missing and choking and just struggling to keep running. It is running very rich to the point of smoking bad. I thought the timing may of changed for some reason and yanked the dist. and found TDC on 1 and stuck it back in and set it to -12 deg. It ran maybe a little better but still smoking like crazy and wanting to stall. When revving it, it sounds great and smooth. I was thinking maybe a vacuum leak, but when i pull the PVC line it leans out and jumps to 2k rpm and is happy. I can also seat the idle mixture screws closed and it won't quite die, it wants to alittle more, but wont. I dont want to go out and buy a new carb.... but i might need to. Does anyone have any ideas? Sorry about the novel.

Thanks

Mark

 

Considering it leans out and idles fine if you pull the PCV line, I'd start there, probably just needs the valve replaced.

 

Also check your vacuum lines. Make sure they are all hooked up like they need to be or if not used capped off.

 

OK... I took the carb back off and put genuine holley needle valves in and double checked the booster gasket and blew out every port... again. Then i readjusted the floats while running, which wasn't very easy with the engine bouncing around. Still blows barrels of smoke and hardly idles. I imagine some of the plugs are fouled by now. I am taking the carb to work to have a friend throw it on his truck and see what it does. What kills me the most is that the truck ran before i took it apart...

Thanks for all of the input.

Mark

 

Did it back fire at all when you first started it up. If it did then you may have blown out the power valve, that'll make it run really rich at idle. Also make sure it's the same size as the original, the # is stamped on the front.